Cannot use VPN in wireless connection

Hello,

I am trying to use VPN on my laptop, which has a wireless connection to my home network (without the VPN this network works fine).
This however does not work, that is: it is trying to connect, but I receive the (by pop-up screen) message:  connection error..

The other (usual) pop-up, which shows e.g. the virtual location, shows also: your connection is insecure.

I have no idea how to overcome this problem, can you help, please?

regards, Hugo